The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Automobile engines produce emissions such as carbon monoxide (CO), volatile organic compounds (VOCs), and nitrogen oxides (NOx). An automobile may include one or more catalytic converters that are designed to reduce these emissions. A catalytic converter includes a plurality of substrates coated with catalysts, such as precious group metals like platinum, rhodium and/or palladium. The structure is designed to expose a maximum surface area of the catalysts to exhaust flowing from the engine thus, reducing a level of emissions in the exhaust through chemical reactions with the catalysts.
Conventional catalytic converters provide a higher density of catalysts in a forward section of the catalytic converter to increase the reduction of emissions. At the same time, conventional converters provide a lower density of catalysts in a distal section of the catalytic converter to decrease cost. More particularly, with reference to FIG. 1, a catalytic converter 10 according to the prior art is shown. The catalytic converter 10 includes an inlet 12 that allows exhaust 14 to enter the catalytic converter 10 and an outlet 16 that allows exhaust 14 to exit the catalytic converter 10.
The catalytic converter 10 includes a first substrate 18 arranged in a first sub-section 20 of the catalytic converter 10 and a second substrate 22 arranged in a second sub-section 24 of the catalytic converter 10. The first substrate 18 includes a first catalyst coating 26. The catalyst coating 26 is evenly distributed at a first density throughout the first substrate 18. The coating 26 generally includes oxidation catalysts such as platinum and palladium. The second substrate 22 includes a second catalyst coating 28. The second catalyst coating 28 is evenly distributed throughout the second substrate 22 at a second density that is less than the first density. The second coating 28 generally includes oxidation and reduction catalysts such as platinum, palladium and rhodium.
This design is a viable trade-off for catalytic converters with lower exhaust temperatures and more lenient emissions standards. With the advent of catalytic converters mounted closer to the engine, resulting in higher exhaust temperatures and faster catalyst warm-up rates, the higher density of catalysts on the front section adds minimal reduction in emissions. Stricter emissions standards generate a need for a greater reduction in emissions without a large increase in the amount of Precious Metals added to the catalysts.